Atomic atrocities (the author replies)

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Atomic Atrocities To the Editor: The undersigned is not known as a prolific "letter-tothe-editor-writer", certainly not when i t concerns hook reviews. I have to say something, however, about the comments by Gordon B. Skinner on the hook by Maron and Lando (J. CHEM. EDUC., 52, A333 (1975)). He states that "the strongest chapters in the text are those on thermodynadics" and "the chapters on atomic and molecular structure are also good". Challenging the first statement is rather fruitless, since the presentation of this subject remains very controversial [see, e.g., the thought-provoking article by Otto Redlich in the same issue, p. 3741. The chapter on atomic structure, however, contains atrocities which should he pointed out. Just to take the worst ones I noticed a t a first dance: . I t . The particular t~aluerof + which yield sarisfnerory, soIutimsuf eqn. 1371 art- called eigenfumfions . . . p. 140: H is a nun-cummtrting operator, ie.:

J. d e Heer University of Colorado Boulder, 80302

For each run, both solutions are poured through the burets into a test tube, shaken and allowed to stand for approximatelv 20 min in a hot water bath. When cool. the heieht of precipitate is measured. The contents of each test tuge are filtered in a filter paper previously weighed on an analytical balance. We have tested the literature procedure," however. we conclude that is not necessarv to ~reviouslvwet the filter paper. After standing overn-ight i n an oven a t 10O0C,the mass of precipitate can be determined by difference. The results are exchanged within the group and each pair of students presents a report a t the beginning of the next laboratory class, a t which time twenty minutes are devoted to a discussion of the data obtained b s them. The heights or masses of precipitates as ordinate values are plotted against the number of moles as ahcissa values, the inflection giving the stoichiometry of the reaction. Although both approaches lead the students to the same conclusion, the mass plotting gives the best result, besides which, it excludes the problem of the presence of floating material and does not depend on the manner in which the precipitate settles by gravity. Another advantage of this experiment comes from the fact that the students can compare various systems a t the same time with readily available chemicals.

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Masaguer, J. R., Victoria toto, M., and Casas, J. S., J. CHEM. EDUC., 52,387 (1975). Investigating Chemical Systems, CBA, Ed. Welster Division, McGraw-Hill Book Company, Experiment 7. Gaddis, Shirley W., J. CHEM. EDUC., 38,5 (1961).

To the Editor:

Claudio Airoldi

Dr. de Heer has raised some questions about the review of the hook by Maron and Lando [52, A 333 (197511. I can only agree that the statements in the text pointed out by Dr. de Heer are poorly phrased. I can appreciate how they might seem "atrocities" to a quantum chemist. I do not know how much trouble these statements will cause students when taken in the context of the discussion in the text and a classroom presentation by the professor. Still, a textbook should be carefully worded so as to avoid imparting any misinformation. Each potential user will have to decide how serious these shortcomings are when combined with the other qualities of the text. Gordon B. Skinner Wright S t a t e University Dayton, Ohio 45431

Continuous Variations To the Editor: This Journal recently published [52, 387(1975)11 modifications introduced in the original procedure2 on the Continuous Variations method. The purpose of this letter is to report our changes and give some idea as to how the method has been used with success in the first year General Chemistry laboratory course as applied to a great number of students. We are pleased to know that the results obtained hy us in 1970 have been confirmed. However, to check the stoichiometry of the reaction we have employed simultaneously the measurement of solid height in the test tube and the mass of precipitate. We have used 0.25 M solutions of Pb(N03h and BaC12, combined with 0.50 M solutions of KI, Na2C03 and K2Cr04. A group consisting of four pairs of students working with a certain couple of salts as established, follows the reaction using the same volume of reagents as described.' 268 / Journal of Chemical Education

Universidade Estadual de Campinas Caixa Postal, 1170 13.100 Campinas, S5o Paula, Brazil

Magic and Science To the Editor: Martin Dines' excellent Provocative Opinion column [J. Chem. Educ., 52, 369 (1975)] underscored the magic in science but failed to mention another aspect of the situation that is often overlooked, oiz., the similarity between the modus operandi of magic and science. In fact, Sir James G. Frazer who regarded magic as "the bastard sister of science," stated1: Sympathetic magic.. . assumes that in nature one event follows another necessarily and invariably without the intervention of any spiritual or personal agency. Thus its fundamental conception is identical with that of modern science; underlying the whale system is a faith.. imolicit . but real and firm. in the order and uniformity of nature. The maeician does not doubt that the same causes will alattended by the desired result. . ." In this sense magic therefore has more in common with science than with religion, which is predicated on belief in a superhuman being or beings who rule the world. Thus the fact that the cave door of the thieves' hideout opens regardless of whoever utters the words "Open, sesame!" is analogous to the successful replication of a given scientific experiment by anyone following the correct procedure. '"The Golden Bough," abridged ed., The Macmillan Co., New York, 1945, pp. 48-9. George B. Kauffman California State University Fresno. 93470